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SubjectRe: [PATCH v3 2/2] dma: pl330: add DMA_PAUSE feature
On Wed, Dec 10, 2014 at 11:55:18AM +0100, Robert Baldyga wrote:
> DMA_PAUSE command is used for halting DMA transfer on chosen channel.
> It can be useful when we want to safely read residue before terminating
> all requests on channel. Otherwise there can be situation when some data
> is transferred before channel termination but after reading residue,
> which obviously results with data loss. To avoid this situation we can
> pause channel, read residue and then terminate all requests.
> This scenario is common, for example, in serial port drivers.
And where is the resume here? Also this needs rebase

--
~Vinod

>
> Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
> ---
> drivers/dma/pl330.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 2f4d561..ead4369 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2137,6 +2137,25 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned
> pm_runtime_mark_last_busy(pl330->ddma.dev);
> pm_runtime_put_autosuspend(pl330->ddma.dev);
> break;
> + case DMA_PAUSE:
> + /*
> + * We don't support DMA_RESUME command because of hardware
> + * limitations, so after pausing the channel we cannot restore
> + * it to active state. We have to terminate channel and setup
> + * DMA transfer again. This pause feature was implemented to
> + * allow safely read residue before channel termination.
> + */
> + pm_runtime_get_sync(pl330->ddma.dev);
> + spin_lock_irqsave(&pch->lock, flags);
> +
> + spin_lock(&pl330->lock);
> + _stop(pch->thread);
> + spin_unlock(&pl330->lock);
> +
> + spin_unlock_irqrestore(&pch->lock, flags);
> + pm_runtime_mark_last_busy(pl330->ddma.dev);
> + pm_runtime_put_autosuspend(pl330->ddma.dev);
> + break;
> case DMA_SLAVE_CONFIG:
> slave_config = (struct dma_slave_config *)arg;
>
> --
> 1.9.1
>

--


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